Electric circuit breaker



Nov. 10, 1953 R, T, CASEY 2,658,973

ELECTRIC CIRCUIT BREAKER Filed Sept. 29, 1949 FIG. 4

e4 INVENTOR. fb n I Robert T. Casey /F 5e BY A 'es 6 60 6 ATTORNEY Patented Nov. 10, 1953 En STATES ENT oFF lie-E.

25658,:173-1- ELECTRIC'CIRCUITB'EKR' Robert TI' Casey,-k B'istoh' Gonn., assigning;Y by" mesme:assiggnmenifs;` mi Generar Electric cani#t pany, a corporation of New'York Applieationseptember 29, 1949, serial'No: 1181518" (Cl:- roo-zsm?y 10i` Claims.' l,

Itis'wellk'nownv that in4 interrupting yalternat` ing currents, a` -great Variationv occursl in tlie "ine tensityfof the arc, the amountof"" fiaineY issuing from the breakerfthedamagetothecasing and' metal parts;v danger tov personnel,v and iire jhaz` ardiduring diierenty interruptions;. diie to the fact that with conventional breakers; theseparation ofjthe contacts and" hence' the vdrawing of, the are, is liable; toV occur. at various points inthe currentzcyrcle: If` ithappens t'o 'occur when the current-'is'.just;,nearingitsi peak;- all of` these factorswill be'at 'or near a maximurr'i. If. it occurs. when the current'is close torero," these facto'rsiwill 'be at aminim'um.

In: the pastthis has depended' entirely onchance;V It is an object'of 'the rpresent'invention to provide' apcircuit breaker'which shall open` at a predeterminedlow point'inl the alternating;

current cycle.

Ithas beenattempted inthe past to make Ya the contacts ratherthan on .the releasir'lg. mecha-4 nisrn. They are. moreover. relatedlto. large oil" breakers. whereas they present 1 inventionl is' an adaptationto. the -simpl structures .of .small `fair circuit` breakers.

Thev drawingsr disclosev amagnetic'ally, respon#` sive: meansffor.releasing.the triplerestraining1 .elefment .of a, .circuit .f breaker. It? will. be: seen from. the nature of this. .and Asimilar. circuit breakers,

that whenin .the foncondition .there isla .constantly maintained force tendingtocauseeaute maticopeningfof. `the contacts. y This forceis restrainedv from actingrbyaf .latch which is mov-.-

able to. a .releasing position vto allow-tripping f. or.

automatic opening .to` occur.

by.otheroverload. responsive action.

The accompanying.. drawing. show I circuitr breakers embodying two forms-of my invention.

Figs. 1 yis a.-face :View of one'form..of-circuitr breaker With. the,parts`in the closed circuit `or on position.

Fig.,v 2 is fa fragmentary cross section takenon the. plane ofthe .line 2`2 .o'f Fig. 1.

Fig..,3 is a face View of. another form of circuit breaker withthe parts' in full lines .in open circuit.

position and jin dotted lines in the closed circuit position;

Fig. 4 is a fragmentary'sectionalyiew v'of the These,IV however, have. attempted'to operate directlyjon sar-y vtotthrow vthe actuating lever l 3 Ttowardth'e' Icradle `ortrip arm l I 'counter-'clockwiseianfcarry Y 45 A the "'hiiige, pointV I 0f'across"the "centerline ofthe spring l5 i'by lwel-1 kn'wrr toggle-eenen ana' thu'sfl' open the' f circuit-f l To release une 1 switch iricaseof-'afheavysurge .of current, I provide 'an' electromagnetic device comprising "a el'd I"piece-2 6' andian armature 2 1 formed v*as a*an ""oppositely4 'extending arrriori the pivoted -lateh' 254;* the "armature" 21" anauat'eh]- lever 25 -constitutirig 'a ,bene crank? pivotedfat za*i onthe trip arm IA l'f" The' conductor" 23' is; clamped between the poles of the magnet 2S by a non-- magnetic plate 29 (Fig. 2) so that the magnet is energized by a heavy current passing between the poles of the magnet clockwise about its pivot support 28. The spring 35 biases the armature away from the magnet and tends to engage the latch with the release catch 2li. Shoulder 3l on the end of the cradle limits the clockwise turning movement of the armature and the latch.

When the magnet is energized the armature 21 is drawn down and the latch 25 released from the catch 24. It will be seen, however, that although the latch 25 is released, the cradle II cannot turn counterclockwise as long as the armature 21 is held Idown by the magnetic force. Spring I5 tends to turn the cradle il countern clockwise. As long as the holding force of the magnet 26 is strong enough to overcome the effect of spring 30 no automatic opening can take place. When the magnetic pull decreases to a point where it is less than the effective pull of spring I5 the cradle II will be released and rotate countercloclcwise and open the circuit.

It is well known that the holding-in force of an electro-magnet greatly exceeds its maximum pull. ln order to taire advantage of this holding-in force, I may provide that the relation between the attractive movement of armature 2".' and the amount of latch overlap at 2d is such that even when the armature 21 is fully in engagement with magnet 25, the latch 25 will not be released until the bimetal 2l moves bach a short distance. With this arrangement, it will be assured that armature 2.1 will engage the magnet 26 before the catch 24 releases the latch 25. The magnetic holding force will then hold the trip arm II against movement even after latch release until the current approaches zero.

By reason of the residual magnetism the hold ing force of the magnet 25 will not reach absolute zero value until the current has reversed its direction and reached some new value. The time which elapses between release of the magnet and opening of the circuit may vary depending upon the weight, inertia and speed of movement of the associated parts. The dimensions and material of the magnet 26 and its armature 2l may in any given case be so chosen therefore that the point in the cycle of current at which the magnet releases will be such that the con tacts will separate at or near the Zero current point. When the magnet 2E iinally releases its armature 21 the cradle or trip arm II is iree to rotate anti-clockwise by the toggle action of spring I5 and switch member (l.

When it is called to mind that the current this type of breaker is normally called upon to interrupt is an alternating current, which is continually varying from a maximum to a cero value, and that even under short circuit conditions a surge of excess current will be followed by a reduction of current to the Zero point, it will be seen that should a short circuit occur while the current is building up to its maximum value, armature 21 will pull in and will hold cradle I I from rotating and hence prevent the contacts from opening until the current again decreases to a value low enough so that the magnetic pull of the magnet is too small to hold the cradle, at which time the cradle will be released.

It will, therefore, be seen that the contacts will open at or near a time when the varying current is zero. The breaker will, therefore, not be called upon to interrupt a high current, nor will there be the characteristic flame and damage Il l) caused by a large arc. The life of the breaker will also be considered lengthened.

lt should be noted that this design also permits the magnetic trip to have the desired release-delaying action without interfering with the no1'- mal operation of the bimetal trip on small overloads.

The form of my invention disclosed in Figs. l and 2 is described and claimed in my copending continuation-in-part application Serial Number 237,256, filed July i7, 1951.

The form shown in Figs. 3 and ll shows a `form of circuit breaker in which a minimum current magnetic tripping action is combined with a manual operation as well as a thermostatic release.

Any suitable circuit terminals such as 36 and 31 may be mounted in the housing 35. The housing 35 is a two-part housing, as is the housing 5 of Fig. 1, the housing parts being suitably recessed to receive the operating parts and each housing member being the mirror image of the other. Stationary contact 33 and movable contact 39 constitute the switch members. The switch member 39 is hinged at 40 in the cradle or tripping member lll which is suitably hinged at l2 in the housing parts 35.

The manually operable handle rocker 43 is hinged at it and connected by spring 45 from 45 on the rocker to the switch member 39 at 41. The handle rocker i3 has a lug l5 for engaging the cradle 5l! and operating the switch by a conventional toggle action.

Terminal 51 has a supporting member 50 suitably secured to the housing 35 to which the upper end of a thermal-responsive bimetal strip 5I is secured and in which a Calibrating screw 52 is adjustable. This strip 5l is connected by a flexible conductor 53 to the hinged switch member' 39.

A magnet field piece 55 is mounted on the strip 5l and consequently moves with it. An armature 55 is hinged at 51 in suitable recesses in the housing halves 55. The spring 58 biases the armature 55 away from the eld piece 55.

A nonemagnetic spring latch member 5I) is supported by member 5S and has a loose connection at 5I with the movable end of bimetal strip 5I the latch member @t being slotted at its lower end to receive the bimetal strip 5I. This latch member @il extends between the armature 55 and the iield piece 55 and has a bent tip 52 forming a latch which extends into normal latching engagement with a shoulder 63 on the end of the cradle 'il (Figs. 3 and ll).

In case of a slow overload the bimetal strip 5I warps toward the bight of the magnet 55, draws over the spring latch member 55 and releases the tip 52 from the cradle lil, the cradle 4l then moving to open the circuit in the usual manner. During this operation the spring 5E! holds the armature to the left against a suitable stop (not shown) formed in the casing 35.

In case of a high current or heavy surge of current, the magnet is energized to draw the armature and latch arm Bil toward the eld piece 55, the armature engaging and moving the lower end of the latch arm lili so as to release the cradle or trip arm 4 l. l'n this case, however, the stop or latch ell on the armature has been moved with the armature to a position in which the latch 64 is interposed in the path of movement of the shoulder 55 on the trip arm l I, and after a slight initial movement upward of the trip arm past the latch 52, the shoulder 55 engages the stop 64 and s brings the trip arm to rest. The trip arm isv held b'ythe shoulder 65ffuntilthe instantaneous K4value rent:"flowsfthroughthe bimetahstrip decreases' suiiiciently toiderenergize thelmagnetandperniit' the spring 58 to move the armature back'to its unattracted -npsitionfsnowri in -Figsf3 andi-tand therebyi'disengage*the stop B4' from the shoulder` force to overco'mcfthe bia cf "the-armature-bias upward inaccordanc iti-bias tov open''tl're'A inthe closedpositio VIhe releasingliaction achieved by this latter structure 1 is fof lthe two-step type. f When a small overload occurs' only lthe rst step isIV necessary in order to release the breaker. When a 'relatively' large =overload-`occurs (sd-as to actuate the"magnet) two steps are necessary, i. e., the main latch must release, and the nauxiliary or secondary latch must release.

I clairnsi "es 1. In a circuit breaker, a trip member biased to an open circuit position, a latch normally holding saidtrip member in a closed circuit position, electromagnetic 'means provided' with an armature. movable 'to'an"attractie'd position in response to a'high current 'in the circuit breaker for moving said latch to release said trip member, and a connection between said armature and said trip member for holding said trip member until said armature is released for movement upon a decrease in current.

2. In a circuit breaker, a trip member biased to an open circuit position, a first latch normally holding said trip member in a closed circuit position, electromagnetic means provided with an armature biased to an unattracted position and movable in response to a high current in the circuit breaker for moving said iirst latch to release said trip member, and a second latch moved by said armature into the path of said trip member so as to restrain said trip member until the current has decreased to permit the return of said armature to its unattracted position.

3. In a circuit breaker, a trip member biased to an open circuit position, a latch member normally restraining said trip member, electromagnetic means responsive to the current in the circuit breaker provided with an armature biased to an unattracted position and movable in response to a high current for moving said rst latch to release said trip member for an initial movement, and a latching projection on said armature for restraining of said trip member until the current has decreased to permit the return of said armature to its unattracted position.

4. In a circuit breaker, a trip member biased to an open circuit position, a latch normally holding said trip member in a closed circuit position, electromagnetic means energized by the current in the circuit breaker provided with an armature biased to an unattracted position, an operating connection between said armature and said latch for moving said latch to release said trip member when said armature is moved to an attracted position in response to a high current, and a second latch moved by said armature to hold said trip member after said trip member is released by said i Ul ' tur'etofar unattracted'positioman operatn co first latch until s aid armaturereturns, to its,l un-l attractedposition` in response to4 a' creas ,u thecurrent inthe' circuit breaker.

5.?v In va circuitl breaker, a member biased to an open lcircuit"'1,Jos`itio'n,` a'latch,v normally; holding said trip member in aj cl'osedcircuitY osi"-y tion, a lmagnet lfield `piece,'means'respo e te thecurrentfin the circuit breaker forenergizing said eld piece, amovably mounted armature for,` said iield piece, a springfor biasingfsaidia nection betweensaidarmature and said latc'hf mving said latch'to rel-ease -'said trip menfirbe'r` when f said.v armaturel is Aiiio'vejd toward," "saidjieldl piece f to an attra'ctedfpositionV "in" response "tbl armaturefinto thepath of, s'aid trip member; wli Y saidi'arm'ature moves `to itsattracted' position so," as to hold saidtrip njil'embei"` after 'it is releas'edfbyfl said first 'latch until" said armature is "moved `by` said springupon aA decrease in the current in' said.. energizing means. A

6: Inj-a circuit breaker, a trip member biased, to anA open circuit position," a spring latch a having av latching projectionfo'r engaging,and"l holding said trip member in a closed circuit position, amagnet field piece, current conducting" energizing Ymeans for said eld vpiece Yconnected 'inv circuit with said circuit breaker, a movably mounted armature for said field piece, a, V for biasing said armature 'to an unattracted p y tion, an operating connection between said larm ture and said latch arm formoving said lato arm `to.releasesa'iol trip member wheny said arma; ture is moved toward said field piece to an attracted position in response to a pre-determined high current, and a projection on said armature movable into the path of said trip member when said armature moves to its attracted position so as to s-top said trip member after an initial movement and hold said trip member until said armature is moved by said spring to its unattracted `position upon a decrease in the instantaneous value of the current in said energizing means.

7. A circuit breaker having circuit making and breaking mechanism, a trip member for said mechanism biased to an open circuit position, a latch arm for holding said trip member, a bimetal thermostatic strip, means for heating said bimetal strip in response to the current in the circuit breaker, a magnet field piece carried by a movable end of said bimetal strip, a spring biased armature for said eld piece for engaging Iand moving said latch arm in response to a high current thereby to release said trip member, a latching projection on said arma-ture movable into the path of said trip member when said armature moves to its attracted position thereby to stop said trip member after an initial movemen and hold said trip member until said armature returns to its unattracted position upon a decrease in current, and an operating connection between said bimetal strip and said latch arm for movement of said latch arm by said bimetal strip in response to a low current in the circuit breaker.

8. A circuit breaker having circuit making and breaking mechanism, a trip member for said mechanism biased to an open circuit position, a spring latch arm having a latching projection for engaging and holding said trip member, a bimetal thermostatic strip, means mounting adjacent ends of said latch arm and said bimetal strip so that they extend in substantial parallel adjacent relation with each other, means for heating said bimetal strip in response to Ithe current in the circuit breaker, a magnet eld piece carried by the movable end of said bimetal strip, a spring biased armature for said eld piece on the opposite side of said latch arm from said iield piece so that said latch arm is engaged by said armature in moving in response to a high current to an attracted position thereby to release said trip member, a latching projection on said armature movable into lthe path of said trip member when said armature moves to its attracted position thereby to stop said trip member after an initial movement and hold said trip member until said armature returns to its unattracted position upon a decrease in current. and an operating connection between said bimetal strip and said latch arm for movement of said latch arm by said bimetal strip in response to a low current in the circuit breaker.

9. In an alternating current circuit breaker having circuit making and breaking mechanism. a movable trip member for said mechanism biased to an open circuit position, latch means including a bimetallic strip heated in response to the current in said circuit breaker, said latch means normally restraining movement of said trip member and releasing said trip member in response to predetermined overload current heating of said bimetallic strip, magnetic means including an armature movable to an attracted position in response to a predetermined overload current to at least partially release said latch means independently of said bimetallic strip and to hold said trip member against movement, said armature moving to an unattracted position upon instantaneous current decay and releasing said trip member for movement to open said circuit breaker.

10. In an alternating current circuit breaker having circuit making and breaking mechanism, a movable trip member for said mechanism biased to an open circuit position, latch means including a bimetallic strip heated in response to the current in said circuit breaker, said latch means normally restraining movement of said trip member and releasing said trip member in response to predetermined overload current heating of said bimetallic strip, magnetic means including an arma-ture movable to an attracted position in response to a predetermined overload current to release said latch means independently of said bimetallic strip and to hold said trip member against movement, said armature moving to an unattracted position upon instanta neous current decay and thereby releasing said trip member for movement to open said circuit breaker.

ROBERT T. CASEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,829,615 Schwennker Oct. 27, 1931 2,184,372 Von Hoorn Dec. 26, 1939 2,447,652 Jennings Aug. 24, 1948 

